1. Technical Field
This invention relates to a roadside-vehicle cooperative illumination system in which a headlight of a vehicle and a road illumination lamp are controlled cooperatively through communications between an in-vehicle apparatus and a roadside apparatus.
2. Related Art
A known road illumination system, as disclosed in Japanese Patent Application Publication No. 2002-305088, controls illumination of a road illuminator as a function of a traffic density so as to reduce power consumption of the road illuminator.
The above disclosed road illumination system includes a road illuminator that illuminates a road, a service marker arranged at a position through which a vehicle that will travel within a region to be illuminated on the road can pass, and a radio tag that receives a radio signal sent from the vehicle when the vehicle has passed through the service marker. The road illuminator is controlled by its controller to reduce or extinguish illumination of its road illumination lamp until the signal from the vehicle is received by the radio tag. Upon reception of the signal from the vehicle, the road illuminator is controlled to illuminate the road illumination lamp with sufficient brightness for a prescribed period of time.
The above disclosed road illumination system is also operative to, upon detection of an obstacle on the road such as a pedestrian, a bicycle, and a vehicle, control the road illumination lamp so as to spotlight the obstacle, or upon occurrence of an accident such as a traffic accident and a disaster, change illumination color of the road illumination lamp or blink the lamp on and off at and around the scene of the accident.
In operation, the above disclosed road illumination system turns on the road illumination lamp of the road illuminator in the presence of a passing vehicle, and dims or turns off the road illumination lamp of the road illuminator in the absence of the passing vehicle, thereby reducing power consumption of the road illuminator. In other words, the above disclosed road illumination system turns on the road illumination lamp only in the presence of the passing vehicle without taking into account a state or condition of the passing vehicle.
For example, in the case of a motor-driven vehicle with a reduced SOC (state of charge) of a vehicle battery that supplies electrical power to the vehicle, lighting of a headlight of the vehicle will consume electrical power of the battery, which may lead to reduction in continuously travelable distance. In such a case, increasing an illuminance and/or an illumination range of the road illumination lamp of the road illuminator to an extent large enough to reliably confirm the safety in a forward direction of the vehicle will allow the illuminance of the headlight of the motor-driven vehicle to be lowered and the power consumption of the lighting headlight to be suppressed. This may minimize reduction in continuously travelable distance and enhance motor-driven vehicle driver's convenience. In addition, to ensure the safety in a forward direction of the vehicle in the absence of sufficient brightness in the forward direction due to a headlight failure, it may be efficient to increase the illuminance of the road illuminator.
That is, when power consumption of the headlight of the vehicle has to be reduced or when it is not possible to ensure a sufficient illuminance of the headlight, the road illumination lamp may be controlled cooperatively with the headlight through the communications between the in-vehicle apparatus and the road illuminator so that illumination of the road illumination lamp can compensate for deficiencies in illumination of the headlight, which will lead to enhancement of the driver's convenience and ensuring of safety.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a roadside-vehicle cooperative illumination system, in which a headlight of a vehicle and a road illumination lamp can be controlled cooperatively through communications between an in-vehicle apparatus and a roadside apparatus.